docs: rename compatibility→supported, add zstd-jni column, CI badge

- docs/compatibility.md → docs/supported.md (+ retitle)
- per-symbol tables gain a zstd-jni column (symbols referenced by its JNI
  sources v1.5.7-11); 53 of 186 vs this lib's 55
- Bindings.java javadoc points to docs/supported.md; drop the duplicated
  inline deprecated-function list (doc is now canonical)
- README: add CI status badge

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dfa1

README.md

@@ -1,5 +1,6 @@
 # zstd-java
 
+[![CI](https://github.com/dfa1/zstd-java/actions/workflows/ci.yml/badge.svg)](https://github.com/dfa1/zstd-java/actions/workflows/ci.yml)
 ![zstd](https://img.shields.io/badge/zstd-1.6.0-green.svg)
 ![Java](https://img.shields.io/badge/Java-25%2B-orange.svg)
 [![License](https://img.shields.io/badge/License-BSD%203--Clause-blue.svg)](LICENSE)